A New Navigation Message Demodulation Algorithm for Satellite Navigation Receiver

A new navigation message demodulation algorithm for satellite navigation software receiver is researched. The detailed phase and frequency information of the carrier are obtained by analyzing the phase angle of the DFT component of the satellite navigation IF signal, and navigation messages are demodulated by adjusting the initial phase of the adjacent data block is π flipped or not. The detailed implementation steps of the method are presented, and the reason of phase angle discontinuity of kernel function is analyzed and compensated. Finally, the method is verified by simulation and actual signal respectively and compared with the traditional phase-locked loop method. The results show that the carrier frequency accuracy of new algorithm can reach 10 Hz, more precise than traditional method; signal tracking can effectively output navigation message information, the method with data block processing to obtain the phase angle is more suitable for software radio ideas. Introduction Since the concept of software receiving radio has been introduced into the design of satellite navigation receiver, satellite navigation software receiver has quickly become a research hotspot due to its flexibility, scalability and economy [1] . The software receiver is divided into two parts: the RF front-end and the baseband signal processing. The baseband signal processing algorithms of the traditional software receiver are mostly based on the frequency-domain FFT capture and phase-locked loop tracking. The second-order PLL is usually used [2-4] . There are also suitable for high dynamic second-order frequency-locked loop auxiliary third-order phase-locked loop structure [5,6] . This article describes a new software receiver algorithm BASS (synchronization block signal adjustment) method. The basic idea was first proposed by the J.B.Y.TUSI in the United States [7] . The algorithm obtains the carrier's fine frequency and navigation information by analyzing the phase angle of the DFT component of the satellite signal. Compared with the traditional software receiver algorithm, the BASS algorithm Effectively suppress noise, capture the carrier frequency is more accurate, simple and quick calculation, more suitable for software and radio methods [8] . Principle of BASS For satellite navigation IF digital signal ( ) x n with C/A code peeled off, the DFT output is